translate/set.go: Add AddFromCommonObject helper

This is a useful function for copying all the fields of one object to the
identically named fields of another object. We add translations prefixed by
fromPrefix and toPrefix, retrieving the subpaths from to.

translate/set.go

@@ -105,6 +105,19 @@ func (ts TranslationSet) AddFromCommonSource(common path.ContextPath, toPrefix p
 	ts.AddTranslation(common, toPrefix)
 }
 
+// AddFromCommonObject adds translations for all of the paths in to. The paths being translated
+// are prefixed by fromPrefix and the translated paths are prefixed by toPrefix.
+// This is useful when we want to copy all the fields of an object to another with the same field names.
+func (ts TranslationSet) AddFromCommonObject(fromPrefix path.ContextPath, toPrefix path.ContextPath, to interface{}) {
+	vTo := reflect.ValueOf(to)
+	vPaths := getAllPaths(vTo, ts.ToTag, true)
+
+	for _, path := range vPaths {
+		ts.AddTranslation(prefixPath(path, fromPrefix.Path...), prefixPath(path, toPrefix.Path...))
+	}
+	ts.AddTranslation(fromPrefix, toPrefix)
+}
+
 // Merge adds all the entries to the set. It mutates the Set in place.
 func (ts TranslationSet) Merge(from TranslationSet) {
 	for _, t := range from.Set {